OV SCOTLAND.

4. Obdurate Clay or Till•

In their original state, clayey soils are, in general, of a hard

and obdurate nature, mixed with ferruginous matters, and, in

that state, are known in Scotland , under the name of Till. Byexposure, manures, and culture, this stubborn earth is reducedand rendered fertile. There are, however, considerable tractsof this species of soil, only partially cultivated in bcotland,and not yet thoroughly improved. It is necessary, theieloie,to consider this as a species of soil, distinct from the fineiclays.

5. Rich or Improved Clay.

The value of clay, as a soil, depends materially on the sub-soil -, for, if this be open, it renders the clay more tractableand productive. A clay soil often contains too large a pro-portion of argil , which is the fine, soft, unctuous part of it, inwhich case it is over-tenacious, and close in the texture; intime of rain too wet, and in dry weather too hard. A suit-able mixture of sand improves it much, and of gravel still more.A proper texture, however, is not the sole object of the far-mer : he also enriches with putrid and calcareous manures,in due succession ; and he is careful to adapt his crops andtillage to this productive soil, which, under good manage-ment, is attended with profit •, but, in bad cultivation, re-quires great labour, and makes no adequate return.

6.. Loam.

This esteemed and most valuable soil, is a fertile mixtureof earthy and other substances. When it has a considerablemixture of clay, it is called a strong or heavy loam. Therichest loams are those which abound most in vegetable earth,and have a just proportion of clay or sand. In general, loamis a soil neither liable to the fault of mere sand, which is tooioose, nor to that of indurated clay, which is too stilf; andnot only the texture of it is proper, but, by containing vege-